Synthesis and characterization of new divalent lanthanide complexes supported by amine bis(phenolate) ligands and their applications in the ring opening polymerization of cyclic esters

D.T. Dugah, Brian Skelton, E.E. Delbridge

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

Treatment of an array of bis(phenol)s H2Lx {Lx = [(−OC6H2(2,4-R)(6-CH2))2 NCH2CH2X], where X = CH2NMe2, NMe2, NEt2, OMe and R = But, Pet where Pet = C(CH3)2Et} with [Ln(N(SiMe3)2)2(THF)2] (Ln = Yb, Sm) in a 1:1 molar ratio in hexanes afforded a multitude of new divalent lanthanide bis(phenolate) complexes: [L2cYb]2 (X = NEt2, R = But) 1, [L2bYb]2 (X = CH2NMe2, R = But) 2, [L3aYb]2 (X = NMe2, R = Pet) 3, [L3bYb]2 (X = OMe, R = Pet) 4, [L2cSm] (X = NEt2, R = But) 5, [L3cYb] (X = NEt2, R = Pet) 6, [L3cSm] (X = NEt2, R = Pet) 7. X-Ray crystallographic analyses of compounds 1 and 3 reveal dimeric, centrosymmetric structures with 5-coordinate ytterbium centers arising from bridging and terminal phenolate groups. A selection of divalent compounds (1, 3, 4, 5, 6 and 7) were tested as catalyst precursors in the polymerization of ε-caprolactone and/or L-lactide which resulted in high molecular weight polymers with PDIs of 1.11–2.81 and 1.13–1.56 for ε-caprolactone and L-lactide respectively. All polymerization studies were performed in either toluene or THF and at room temperature (ε-caprolactone) or 70 °C (L-lactide) at a variety of catalyst:monomer ratios (1:100–1:300). Kinetics analyses of the polymerization of L-lactide by compounds 1 and 5 indicated pseudo-first order response with respect to L-lactide.
Original languageEnglish
Pages (from-to)1436-1445
JournalDalton Transactions
Volume2009
Issue number8
DOIs
Publication statusPublished - 2009

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